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United States Patent |
6,195,469
|
Nishioka
,   et al.
|
February 27, 2001
|
Image processing apparatus for shading correction
Abstract
An image processing apparatus includes a shading data calculating section
for two-dimensionally mapping digitized data obtained by
photo-electrically detecting uniform light converged by a lens by a
two-dimensional sensor, thereby producing two-dimensional shading data
whose density signal levels ellipse-like lower outwardly from a center
pixel corresponding to the center of the lens to produce one-dimensional
shading data from the density signal levels of the two-dimensional shading
data on an arbitrary straight line extending outwardly from the center of
the center pixel and calculating the angle .theta. between the straight
line used for producing the one-dimensional shading data and the longer
axis of the ellipse and the ratio of the longer axis to the shorter axis
of the ellipse, a shading data memory for storing the one-dimensional
shading data, the angle .theta. and the ratio of the longer axis to the
shorter axis of the ellipse, a shading correction data producing section
for producing shading correction data of each pixel based on the
one-dimensional shading data, the angle .theta. and the ratio of the
longer axis to the shorter axis of the ellipse stored in the shading data
memory in accordance with distance between the center of the center pixel
and itself and an angle between a straight line passing through the center
of the center pixel and itself and the longer axis of the ellipse and a
shading correcting section for correcting shading of image data based on
the shading correction data. According to the thus constituted image
processing apparatus, it is possible to simply correct the shading of an
image produced by a two-dimensional sensor by converging onto the
two-dimensional sensor light through a lens.
Inventors:
|
Nishioka; Yukinori (Kanagawa-ken, JP);
Umeda; Tomoaki (Kanagawa-ken, JP)
|
Assignee:
|
Fuji Photo Film Co., Ltd. (Kanagawa-ken, JP)
|
Appl. No.:
|
140753 |
Filed:
|
August 25, 1998 |
Foreign Application Priority Data
Current U.S. Class: |
382/274; 358/461; 382/312 |
Intern'l Class: |
G06K 009/40; G06K 009/20; H04N 001/40 |
Field of Search: |
382/312,254,274,167,275
348/251,254
358/461,518,519,521
|
References Cited
U.S. Patent Documents
3919473 | Nov., 1975 | Cotter | 348/251.
|
4343021 | Aug., 1982 | Frame | 348/251.
|
4754332 | Jun., 1988 | Bergquist | 348/576.
|
5327247 | Jul., 1994 | Osborne et al. | 348/251.
|
5703671 | Dec., 1997 | Narita et al. | 355/32.
|
5724456 | Mar., 1998 | Boyack et al. | 382/274.
|
Foreign Patent Documents |
59-161177 | Sep., 1984 | JP | .
|
Primary Examiner: Lee; Thomas D.
Assistant Examiner: Chen; Wen Peng
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak & Seas, PLLC
Claims
What is claimed is:
1. An image processing apparatus comprising shading data calculating means
for two-dimensionally mapping digitized data obtained by
photo-electrically detecting uniform light converged by a lens by a
two-dimensional sensor, thereby producing two-dimensional shading data
whose density signal levels lower outwardly and elliptically from a center
pixel of an ellipse corresponding to the center of the lens to produce
one-dimensional shading data from the density signal levels of the
two-dimensional shading data on an arbitrary straight line extending
outwardly from the center of the center pixel and calculating an angle
.theta. between the straight line used for producing the one-dimensional
shading data and a longer axis or a shorter axis of the ellipse and a
ratio of the longer axis to the shorter axis of the ellipse or the shorter
axis to the longer axis of the ellipse, shading data storing means for
storing the one-dimensional shading data, the angle .theta. and the ratio
of the longer axis to the shorter axis of the ellipse or the shorter axis
to the longer axis of the ellipse, shading correction data producing means
for producing shading correction data of each pixel based on the
one-dimensional shading data, the angle .theta. and the ratio of the
longer axis to the shorter axis of the ellipse or the shorter axis to the
longer axis of the ellipse stored in the shading data storing means in
accordance with distance between the center of the center pixel and said
each pixel and an angle between a straight line passing through the center
of the center pixel and said each pixel and the longer or the shorter axis
of the ellipse and shading correcting means for correcting shading of
image data based on the shading correction data.
2. An image processing apparatus in accordance with claim 1 wherein the
image processing apparatus further comprises bit number converting means
for increasing the bit number of image data corrected by the shading
correcting means.
3. An image processing apparatus, comprising:
a lens;
a photo-electric sensor which receives light from said lens;
a shading correction processor which two-dimensionally maps digitized data
obtained from said photo-electric sensor, thereby producing
two-dimensional shading data whose density signal levels are lowered
outwardly and elliptically from a center pixel of an ellipse corresponding
to the center of the lens, said processor further producing
one-dimensional shading data from the density signal levels of the
two-dimensional shading data based on an arbitrary straight line extending
outwardly from the center of the center pixel, and calculating an angle
.theta. between the straight line used for producing the one-dimensional
shading data and a longer axis or a shorter axis of the ellipse;
a shading data memory which stores the one-dimensional shading data and the
angle .theta.;
a shading correction data producer which produces shading correction data
for each pixel of said photo-electric sensor based on the one-dimensional
shading data and the angle .theta. stored in said shading data memory, the
shading correction data being produced in accordance with a distance
between the center of the center pixel and said each pixel of said
photo-electric sensor and an angle defined between a straight line passing
through the center of the center pixel and said each pixel of said
photo-electric sensor and the longer or the shorter axis of the ellipse;
and
a shading corrector which corrects the shading of image data based on the
shading correction data.
4. The image processing apparatus according to claim 3, further comprising
a bit number converter which increases a bit number of image data
corrected by the shading corrector.
5. The image processing apparatus according to claim 3, wherein said shade
correction processor further produces the one-dimensional shading data in
accordance with a ratio of a longer axis to the shorter axis of the
ellipse to a shorter axis of the ellipse or an inverse of the ratio, and
wherein said shading correction data producer further produces the shading
correction data in accordance with the ratio of the longer axis to the
shorter axis of the ellipse or an inverse of the ratio.
6. The image processing apparatus according to claim 5, further comprising
a bit number converter which increases a bit number of image data
corrected by the shading corrector.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus and,
particularly, to such an apparatus which can simply correct the shading of
an image produced by a two-dimensional sensor by converging light onto the
two-dimensional sensor through a lens.
DESCRIPTION OF THE PRIOR ART
A chemiluminescence detecting system is known, which comprises the steps of
selectively labeling a fixed high molecular substance such as a protein or
a nucleic acid sequence with a labeling substance which generates
chemiluminescent emission when it contacts a chemiluminescent substance,
contacting the high molecular substance selectively labeled with the
labeling substance and the chemiluminescent substance, photoelectrically
detecting the chemiluminescent emission in the wavelength of visible light
generated by the contact of the chemiluminescent substance and the
labeling substance and producing digital image signals, effecting image
processing thereon, and reproducing a chemiluminescent image on a display
means such as a CRT or a recording material such as a photographic film,
thereby obtaining information relating to the high molecular substance
such as genetic information.
Further, a fluorescence system using a fluorescent substance as a labeling
substance is known. According to this system, it is possible to study a
genetic sequence, the expression level of a gene and to effect separation
or identification of protein or estimation of the molecular weight or
properties of protein or the like. For example, this system can perform a
process including the steps of distributing a plurality of DNA fragments
on a gel support by means of electrophoresis after a fluorescent dye was
added to a solution containing a plurality of DNA fragments to be
distributed or distributing a plurality of DNA fragments on a gel support
containing a fluorescent dye or dipping a gel support on which a plurality
of DNA fragments have been distributed by means of electrophoresis in a
solution containing a fluorescent dye, thereby labeling the
electrophoresed DNA fragments, exciting the fluorescent dye by a
stimulating ray to cause it to release fluorescent light, detecting the
released fluorescent light to produce an image and detecting the
distribution of the DNA fragments on the gel support. This system can also
perform a process including the steps of distributing a plurality of DNA
fragments on a gel support by means of electrophoresis, denaturing the DNA
fragments, transferring at least a part of the denatured DNA fragments
onto a transfer support such as a nitrocellulose support by the
Southern-blotting method, hybridizing a probe prepared by labeling target
DNA and DNA or RNA complementary thereto with the denatured DNA fragments,
thereby selectively labeling only the DNA fragments complementary to the
probe DNA or probe RNA, exciting the fluorescent dye by a stimulating ray
to cause it to release fluorescent light, detecting the released
fluorescent light to produce an image and detecting the distribution of
the target DNA on the transfer support. This system can further perform a
process including the steps of preparing a DNA probe complementary to DNA
containing a target gene labeled by a labeling substance, hybridizing it
with DNA on a transfer support, combining an enzyme with the complementary
DNA labeled by a labeling substance, causing the enzyme to contact a
fluorescent substance, transforming the fluorescent substance to a
fluorescent substance having fluorescent light releasing property,
exciting the thus produced fluorescent substance by a stimulating ray to
release fluorescent light, detecting the fluorescent light to produce an
image and detecting the distribution of the target DNA on the transfer
support. This fluorescence detecting system is advantageous in that a
genetic sequence or the like can be easily detected without using a
radioactive substance.
In the case where such chemiluminescent light or fluorescent light is
converged onto the photo-electrical surface of a CCD camera by a lens to
take a picture of a chemiluminescent image or a fluorescent image, the
amount of light transmitted through the periphery portion of the lens is
smaller than that through other portions of the lens. Shading is therefore
generated in the image produced by the CCD camera. This makes it necessary
to correct the thus generated shading by data processing.
However, since the shading is generated two-dimensionally and the shading
has to be corrected using two-dimensional correction data, the volume of
the correction data inevitably becomes great so that a memory having great
capacity is needed.
A similar problem occurs not only in the case of correcting the shading in
a chemiluminescent image or a fluorescent image but also in the case of
correcting shading in an image produced by a two-dimensional sensor by
converging light by a lens onto the two-dimensional sensor.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention is to provide an image
processing apparatus which can simply correct the shading of an image
produced by a two-dimensional sensor by converging light onto the
two-dimensional sensor through a lens.
The above other objects of the present invention can be accomplished by an
image processing apparatus comprising shading data calculating means for
two-dimensionally mapping digitized data obtained by photo-electrically
detecting uniform light converged by a lens by a two-dimensional sensor,
thereby producing two-dimensional shading data whose density signal levels
ellipse-like lower outwardly from a center pixel corresponding to the
center of the lens to produce one-dimensional shading data from the
density signal levels of the two-dimensional shading data on an arbitrary
straight line extending outwardly from the center of the center pixel and
calculating an angle .theta. between the straight line used for producing
the one-dimensional shading data and a longer axis or a shorter axis of
the ellipse and a ratio of the longer axis to the shorter axis of the
ellipse or the shorter axis to the longer axis of the ellipse, shading
data storing means for storing the one-dimensional shading data, the angle
.theta. and the ratio of the longer axis to the shorter axis of the
ellipse or the shorter axis to the longer axis of the ellipse, shading
correction data producing means for producing shading correction data of
each pixel based on the one-dimensional shading data, the angle .theta.
and the ratio of the longer axis to the shorter axis of the ellipse or the
shorter axis to the longer axis of the ellipse stored in the shading data
storing means in accordance with distance between the center of the center
pixel and itself and an angle between a straight line passing through the
center of the center pixel and itself and the longer axis or the shorter
axis of the ellipse and shading correcting means for correcting shading of
image data based on the shading correction data.
The inventors of the present invention conducted a study for accomplishing
the above object of the present invention and, as a result, found that
shading is generated in an image produced by a two-dimensional sensor, the
density signal levels of which ellipse-like lower from the center of the
center pixel corresponding to the center of a lens depending on the
convergence characteristics of the lens, and the shape and arrangement of
the photo-electrical elements of the two-dimensional sensor. Therefore,
according to the present invention, digitized data obtained by
photo-electrically detecting uniform light converged by a lens by a
two-dimensional sensor are two-dimensionally mapped by the shading data
calculating means, thereby producing the two-dimensional shading data, and
one-dimensional shading data is produced from the density signal levels of
the two-dimensional shading data on an arbitrary straight line extending
outwardly from the center of the center pixel. The angle .theta. between
the straight line used for producing the one-dimensional shading data and
the longer axis or the shorter axis of the ellipse and the ratio of the
longer axis to the shorter axis of the ellipse or the shorter axis to the
longer axis of the ellipse are calculated and are stored in the shading
data storing means together with the one-dimensional shading data. Shading
correction data for each pixel are produced by the shading correction data
producing means based on the one-dimensional shading data, the angle
.theta. and the ratio of the longer axis to the shorter axis of the
ellipse or the shorter axis to the longer axis of the ellipse stored in
the shading data storing means in accordance with distance between the
center of the center pixel and itself and the angle between a straight
line passing through the center of the center pixel and itself and the
longer axis or the shorter axis of the ellipse and the shading of image
data is corrected by the shading correcting means using the thus obtained
shading correction data. Therefore, since the shading of image data can be
corrected by storing only one-dimensional shading data, it is possible to
obtain an image in which the shading has been corrected using a memory
having small capacity.
In a preferred aspect of the present invention, the image processing
apparatus further comprises bit number converting means for increasing the
bit number of image data corrected by the shading correcting means.
Since the amount of light transmitted through the peripheral portion of the
lens is small, the pixels corresponding to the peripheral portion of the
lens are produced so as to have density signal levels lower than those
they should inherently have. However, since the density signal levels
thereof become higher owing to the shading correction, the density levels
of the pixels recorded so as not to be saturated may be saturated and
become impossible to record. Therefore, according the preferred aspect of
the present invention, the bit number converting means for increasing the
bit number of image data is provided to effectively prevent the density
signal levels of pixels from being saturated and made impossible to record
by the shading correction.
The above and other objects and features of the present invention will
become apparent from the following description made with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic front view showing an image producing system
including an image processing apparatus which is a preferred embodiment of
the present invention.
FIG. 2 is a schematic longitudinal cross sectional view showing a cooled
CCD camera.
FIG. 3 is a schematic vertical cross sectional view showing a dark box.
FIG. 4 is a block diagram of a personal computer and peripheral devices
thereof.
FIG. 5 is a block diagram showing the details of an image processing means.
FIG. 6 is a diagram showing one example of one-dimensional shading data
produced along the longitudinal axis of an ellipse from the center
coordinate.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in FIG. 1, an image producing system includes a cooled CCD camera
1, a dark box 2 and a personal computer 3. The personal computer 3 is
equipped with a CRT 4 and a keyboard 5.
FIG. 2 is a schematic longitudinal cross sectional view showing the cooled
CCD camera 1.
As shown in FIG. 2, the cooled CCD camera 1 includes a CCD 6, a heat
transfer plate 7 made of metal such as aluminum, a Peltier element 8 for
cooling the CCD 6, a shutter 9 disposed in front of the CCD 6, an A/D
converter 10 for converting analog image data produced by the CCD 6 to
digital image data, an image data buffer 11 for temporarily storing image
digitized by the AID converter 10, data storing means 12 for storing
digital image data together with imaging conditions under which the image
data was produced and a camera control circuit 13. An opening formed
between the dark box 2 and the cooled CCD camera 1 is closed by a glass
plate 14 and the periphery of the cooled CCD camera 1 is formed with heat
dispersion fins 15 over substantially half its length for dispersing heat.
The date storing means 12 is controlled by the camera control circuit 13
so as to be accessible.
A camera lens 16 disposed in the dark box 2 is mounted on the front surface
of the glass plate 14 disposed in the cooled CCD camera 1.
FIG. 3 is a schematic vertical cross sectional view showing a dark box 2.
As shown in FIG. 3, the dark box 2 is equipped with a blue light emitting
diode stimulating ray source 21 for emitting a stimulating ray whose
center wavelength is 450 nm. A filter 24 is adhered to the upper surface
of the blue light emitting diode stimulating ray source. The filter 24
cuts light of wavelengths other than one in the vicinity of 450 nm and
harmful to the stimulation of a fluorescent substance and transmit light
having a wavelength in the vicinity of 450 nm. A filter 27 for cutting the
stimulating ray having a wavelength in the vicinity of 450 nm is
detachably provided on the front surface of the camera lens 16. A
diffusion plate 28 is mounted on the upper surface of the filter 24 for
diffusing a stimulating ray emitted from the blue light emitting diode
stimulating ray source 21.
FIG. 4 is a block diagram of the personal computer 3 and peripheral devices
thereof.
As shown in FIG. 4, the personal computer 3 includes a CPU 30 for
controlling the exposure of the cooled CCD camera 1, an image data
transferring means 31 for reading the image data produced by the cooled
CCD camera 1 from the image data buffer 11, an image processing means 33
for effecting image processing on the image data read out by the image
transferring means 31 and storing them in an image data storing means 32,
an image displaying means 34 for displaying a visual image on the screen
of the CRT 4 based on the image data stored in the image data storing
means 32, and an image data analyzing means 35 for analyzing the image
data stored in the image data storing means 32. The blue light emitting
diode stimulating ray source 21 is controlled by a light source control
means 36 and an instruction signal can be input via the CPU 30 to the
light source control means 36 through the keyboard 5. The CPU 30 is
constituted so as to output various signals to the camera controlling
circuit 13 of the cooled CCD camera 1. The image data storing means 32 is
constituted so as to store image data together with imaging conditions
under which the image data was produced and is accessible by the CPU 30.
The image processing apparatus according to this embodiment is constituted
so as to detect fluorescent light emitted from an image carrier carrying a
fluorescent image and a chemiluminescent light released by the contact of
a chemiluminescent substance and a labeling substance and produce a
fluorescent image and a chemiluminescent image and produces a visible
image by detecting fluorescent light emitted from an image carrier
carrying a fluorescent image in the following manner. As termed in this
specification, an image carrier carrying an image of a fluorescent
substance includes an image carrier carrying an image of a specimen
labeled with a fluorescent substance and an image carrier carrying an
image of a fluorescent substance obtained by combining enzyme with a
labeled specimen, contacting the enzyme and a fluorescent substrate,
thereby changing the fluorescent substrate to a fluorescent substance
capable of emitting fluorescent light.
An image carrier 18, which is a specimen, is first placed on the diffusing
plate 28 and the lens focus is adjusted by the user. After the dark box 2
has been closed, the user inputs an exposure start signal through the
keyboard 5. The blue light emitting diode stimulating ray source 21 is
turned on by the light source control means 36, thereby emitting a
stimulating ray toward the image carrier 18 placed on the diffusion plate
28. At the same time, the exposure start signal is input through the CPU
30 to the camera controlling circuit 13 of the cooled CCD camera 1 and the
shutter 9 is opened by the camera controlling circuit 13, thereby starting
the exposure of the CCD 6.
Light components of wavelengths not in the vicinity of 450 nm are cut by
the filter 27 from the stimulating ray emitted from the blue light
emitting diode stimulating ray source 21. As a result, the fluorescent
substance contained in the image carrier 18 is stimulated by light having
a wavelength in the vicinity of 450 nm, thereby emitting fluorescent
light.
The fluorescent light emitted from the fluorescent substance contained in
the image carrier 18 impinges on the photo-electrical surface of a
photo-electrical sensor of the CCD 6 through the filter 27 and the camera
lens 16 and forms an image thereon. The photo-electrical sensor of the CCD
6 receives light of the thus formed image and accumulates it in the form
of electric charges therein. Since the stimulating ray having a wavelength
in the vicinity of 450 nm is cut by the filter 27, only fluorescent light
emitted from a fluorescent substance contained in the image carrier 18 is
received by the CCD 6.
When a predetermined exposure time has passed, the CPU 30 outputs an
exposure completion signal to the camera controlling circuit 13 of the
cooled CCD camera 1. When the camera controlling circuit 13 receives the
exposure completion signal from the CPU 30, it transfers the analog image
data accumulated in the CCD 6 in the form of electric charge to the A/D
converter 10 to cause the A/D converter 10 to digitize the image data to
digital image data of fourteen bits and temporarily store the thus
digitized image data in the image data buffer 11 together with the imaging
conditions. The image data and the imaging conditions under which the
image data was produced temporarily stored in the image data buffer 11 are
input in the data storing means 12 and stored therein. At the same time,
the CPU 30 outputs a data transfer signal to the image data transferring
means 31 to cause it to read out the digital image data temporarily stored
in the image data buffer 11 of the cooled CCD camera 1 together with the
imaging conditions and to input them to the image processing means 33.
However, the intensity of fluorescent light emitted from the image carrier
18 and converged onto the photo-electrical surface of the photo-electrical
sensor of the CCD 6 by the camera lens 16 becomes higher toward the center
of the camera lens 16 since the amount of light transmitted through the
peripheral portion of the camera lens 16 is smaller and, therefore,
two-dimensional shading is generated in the thus produced image data input
to the image processing means 33. Accordingly, prior to displaying a
fluorescent image on the screen of the CRT 4 based on the image data, it
is indispensable to effect shading correction processing on the image
data.
In this embodiment, therefore, correction data for correcting shading have
been produced and stored in the image processing means 33 prior to reading
a fluorescent image and when the image data is input, the image processing
means 33 effects shading correction processing on the image data in
accordance with the correction data for correcting shading and stores the
corrected image data in the image data storing means 32. Afterward, when
the user inputs an image production signal through the keyboard 5, the
image data stored in the image data storing means 32 are read out by the
image displaying means 34 and a fluorescent image is displayed on the
screen of the CRT 4 based on the read-out image data.
Since the shading generated by the camera lens 16 is two-dimensional,
two-dimensional correction data are necessary for correcting the shading.
However, a memory having great capacity is required for storing
two-dimensional correction data and this is uneconomical. Therefore, the
inventors focused on the fact that the shading generated by the camera
lens 16 in the image data are theoretically symmetrical with respect to
the pixel corresponding to the center of the camera lens 16 and that
shading correction data required for each pixel vary in accordance with
distance from the center of the center pixel corresponding to the center
of the camera lens 16. Thus, they found that the shading of image data can
be corrected using a memory having small capacity by obtaining
one-dimensional image data for storage in the memory and correcting the
shading of each pixel of the image data in accordance with distance from
the center of the center pixel corresponding to the center of the camera
lens 16 using the thus stored shading correction data. However, as a
result of the inventors' further investigation, it was found that when
image data are produced by receiving light converged by the camera lens 16
by the photo-electrical sensor, the density signal level of each pixel of
the image data is lowered not circularly but ellipse-like with respect to
the center of the camera lens 16 due to the shape and arrangement of
individual photo-electrical elements of the photo-electrical sensor of the
CCD 6.
Therefore, in this embodiment, light emitted from the blue light emitting
diode stimulating ray source 21, transmitted through the filter 24 and
diffused by the diffusion plate 28 is converged onto the photo-electrical
surface of the photo-electrical sensor of the CCD 6 and photo-electrically
converted to obtain image data. The thus obtained image data are
two-dimensionally mapped to produce two-dimensional shading data whose
density signal levels are ellipse-like lowered outwardly from the center
pixel corresponding to the center of the camera lens 16. One-dimensional
shading data is obtained based on the two-dimensional shading data along
the straight line outwardly extending from the center of the center pixel
and the angle .theta. between the straight line used for obtaining the
one-dimensional shading data and the longer axis of the ellipse and the
ratio of the longer axis to the shorter axis of the ellipse are
calculated, thereby storing the one-dimensional shading data, the angle
.theta. and the ratio of the longer axis to the shorter axis of the
ellipse in a memory. Shading correction data for each pixel are produced
based on the one-dimensional shading data, the angle .theta. and the ratio
of the longer axis to the shorter axis of the ellipse stored in the memory
in accordance with the distance between each pixel and the center of the
center pixel and the angle between a straight line drawn from the center
of the center pixel and the longer axis of the ellipse and the density
signal level of each pixel of the image data is corrected based on the
thus produced shading correction data.
FIG. 5 is a block diagram showing the details of the image processing means
33.
As shown in FIG. 5, the image processing means 33 includes a data
processing section 40 for effecting image processing on the input image
data, a shading data memory 41 for storing shading data, the angle .theta.
and the ratio of the longer axis to the shorter axis of the ellipse, a
shading correction data producing section 42 for producing shading
correction data based on the shading data, the angle .theta. and the ratio
of the longer axis to the shorter axis of the ellipse stored in the
shading data memory 41 in accordance with the distance between each pixel
and the center of the pixel corresponding to the center of the camera lens
16 and the angle between a straight line drawn from the center of the
center pixel and the longer axis of the ellipse, and a bit number
converting section 43 for converting the bit number of shading-corrected
image data from 14 bits to 16 bits so as to prevent the density signal
levels of the pixels which have been produced so that the density signal
levels thereof cannot be saturated from being saturated by the shading
correction.
The thus constituted image processing means 33 effects shading correction
in the following manner in the case of producing a fluorescent image by
exciting an image carrier 18 using the blue light emitting diode
stimulating ray source 21.
After the filter 27 has been removed, if the user inputs through the
keyboard 5 an instruction requesting that the image carrier 18 be excited
using the blue light emitting diode stimulating ray source 21 and that
shading correction data be produced, the CPU 30 outputs a shading
correction data production starting signal to the light source control
means 36 to cause it to turn on the blue light emitting diode stimulating
ray source 21. At the same time, the shading correction data production
starting signal is input through the CPU 30 to the camera controlling
circuit 13 of the cooled CCD camera 1, whereby the camera controlling
circuit 13 opens the shutter 9 to start the exposure of the CCD 6.
Light components of wavelengths not in the vicinity of 450 nm are cut by
the filter 24 from the stimulating ray emitted from the blue light
emitting diode stimulating ray source 21 and the light passes through the
diffusion plate 28, thereby being converted to uniform light and is
converged onto the photo-electrical surface of the photo-electrical sensor
of the CCD 6. The photo-electrical sensor of the CCD 6 receives the thus
converged light and accumulates it as electrical charge.
When a predetermined exposure time has passed, the CPU 30 outputs a shading
correction data production completion signal to the camera controlling
circuit 13 of the cooled CCD camera 1. When the camera controlling circuit
13 receives the shading correction data production completion signal from
the CPU 30, it transfers the analog image data accumulated in the CCD 6 in
the form of electric charge to the A/D converter 10 to cause the A/D
converter 10 to digitize the image data to digital image data of fourteen
bits and temporarily store the thus digitized image data in the image data
buffer 11 together with the kind of light source used for producing the
image data. The two-dimensional shading data and the kind of light source
temporarily stored in the image data buffer 11 are input to the data
storing means 12 and stored therein. At the same time, the CPU 30 outputs
a data transfer signal to the image data transferring means 31 to cause it
to read out the two-dimensional shading data temporarily stored in the
image data buffer 11 of the cooled CCD camera 1 together with the kind of
light source and to input them to the data processing section 40 of the
image processing means 33.
The data processing section 40 of the image processing means 33
two-dimensionally maps the input two-dimensional shading data to produce
two-dimensional shading data whose density signal levels are lowered from
the center pixel corresponding to the center of the camera lens 16
outwardly. Since the photo-electrical sensor of the CCD 6 is rectangular,
the thus mapped two-dimensional shading data are also of rectangular
shape. The data processing section 40 then produces one-dimensional
shading data from the density signal levels of the two-dimensional shading
data on a straight line diagonally extending from the center of the center
pixel, calculates the angle .theta. between the straight line used for
producing the one-dimensional shading data and the longer axis of the
ellipse and the ratio of the longer axis to the shorter axis of the
ellipse and stores them in the shading data memory 41 together with the
kind of light source used for producing the two-dimensional shading data,
namely, the blue light emitting diode stimulating ray source 21. FIG. 6 is
a diagram showing one example of the one-dimensional shading data produced
by the data processing section 40.
When the image data obtained by exciting the image carrier 18 with the
stimulating ray emitted from the blue light emitting diode stimulating ray
source 21 and photo-electrically reading fluorescent light emitted from
the image carrier 18 upon being excited by the photo-electrical sensor of
the CCD 6 are input to the data processing section 40 of the image
processing means 33, the data processing section 40 outputs a correction
data production signal to the shading correction data producing section 42
and causes it read out the one-dimensional shading data, the angle .theta.
and the ratio of the longer axis to the shorter axis of the ellipse stored
in the shading data memory 41.
The shading correction data producing section 42 produces data for
correcting the shading of each pixel based on the one-dimensional shading
data, the angle .theta. and the ratio of the longer axis to the shorter
axis of the ellipse stored in the shading data memory 41 in accordance
with the distance from the center of the pixel corresponding to the center
of the camera lens 16 to each pixel constituting the image data and the
angle between a straight line drawn from the center of the pixel
corresponding to the center of the camera lens 16 to each pixel and the
longer axis of the ellipse and outputs them to the data processing section
40.
The data processing section 40 corrects the shading of the input image data
by multiplying the data for correcting the shading of each pixel produced
by the shading correction data producing section 42 by the density signal
level of the corresponding pixel and outputs the corrected image data to
the bit number converting section 43.
Since the amount of light transmitted through the peripheral portion of the
camera lens 16 is small, the pixels corresponding to the peripheral
portion of the camera lens 16 are produced so as to have density signal
levels lower than those they should inherently have. However, since the
density signal levels thereof become higher owing to the shading
correction, the density levels of the pixels recorded so as not to be
saturated may become saturated and impossible to record. Therefore, in
this embodiment, image data on which the shading correction has been
effected are input to the bit number converting section 43 where the
shading corrected image data of fourteen bits are converted to image data
of sixteen bits, thereby preventing the density signal levels of the
pixels from being saturated and made impossible to record due to the
shading correction. The thus bit number-converted image data are output
from the bit number converting section 43 to the image data storing means
32 and stored therein.
After the shading correction has been effected on the image data and the
image data have been stored in the image data storing means 33 in this
manner, if the user inputs an image production signal through the keyboard
5, the image displaying means 34 reads out the image data stored in the
image data storing means 32 and a fluorescent image is displayed on the
screen of the CRT 4 based on the read-out image data.
Further, if the user inputs an analysis signal through the keyboard 5, the
image data analyzing means 35 reads out the image data and the imaging
conditions under which the image data were produced from the image data
storing means 32 and analyzes of the image data specified by the user. The
result of the analysis is displayed on the screen of the CRT 4.
In the case of producing a chemiluminescent image, a chemiluminescent image
is produced by photo-electrically detecting chemiluminescent emission
emitted from an image carrier 18 by the contact of a chemiluminescent
substance and a labeling substance. Therefore, similarly to the production
of a fluorescent image using the blue light emitting diode stimulating ray
source 21 which is a transmission-type light source, one-dimensional
shading data, the angle .theta. between the straight line used for
producing the one-dimensional shading data and the longer axis of the
ellipse and the ratio of the longer axis to the shorter axis of the
ellipse are obtained and stored in the shading data memory 41 and the
shading correction is performed based on the one-dimensional shading data,
the angle .theta. and the ratio of the longer axis to the shorter axis of
the ellipse stored in the shading data memory 41. Alternatively, if
one-dimensional shading data produced using the blue light emitting diode
stimulating ray source 21, the angle .theta. and the ratio of the longer
axis to the shorter axis of the ellipse have been already stored in the
shading data memory 41, the shading correction is performed using data
stored in the shading data memory 41.
When a chemiluminescent image is to be produced, after one-dimensional
shading data, the angle .theta. between the straight line used for
producing the one-dimensional shading data and the longer axis of the
ellipse and the ratio of the longer axis to the shorter axis of the
ellipse have been obtained and stored in the shading data memory 41,
chemiluminescent emission emitted from an image carrier 18 is
photo-electrically detected via the camera lens 16 by the photo-electrical
sensor of the CCD 6 and digitized to produce image data similarly to the
production of a fluorescent image except that the filter 27 is removed,
that the image carrier 18 for emitting chemiluminescent emission is set in
place and that chemiluminescent emission is detected while the blue light
emitting diode stimulating ray source 21 is kept off. The image processing
means 33 effects the shading correction on the thus obtained image data
using the one-dimensional shading, the angle .theta. and the ratio of the
longer axis to the shorter axis of the ellipse already stored in the
shading data memory 41, similarly to the production of a fluorescent
image, and after the bit number of the image data has been converted from
fourteen bits to sixteen bits, the image data is stored in the image data
storing means 33. Afterward, if the user inputs an image production signal
through the keyboard 5, the image data stored in the image data storing
means 33 are read out by the image displaying means 34 and a
chemiluminescent image is displayed on the screen of the CRT 4 based on
the read out image data.
According to the above described embodiment, the shading of image data can
be corrected by storing only one-dimensional shading data, the angle
.theta. between the straight line used for producing the one-dimensional
shading data and the longer axis of the ellipse and the ratio of the
longer axis to the shorter axis of the ellipse. Therefore, the shading of
image data can be corrected using a memory having small capacity that is
low in cost. Further, according to the above described embodiment, since
the bit number of the image data produced with fourteen bits and
shading-corrected is converted to sixteen bits by the bit number
converting section 43, the density signal levels of pixels produced
without being saturated can be prevented from being saturated and made
impossible to record by effecting shading correction thereon.
The present invention has thus been shown and described with reference to a
specific embodiment. However, it should be noted that the present
invention is in no way limited to the details of the described
arrangements but changes and modifications may be made without departing
from the scope of the appended claims.
For example, in the above described embodiment, one-dimensional shading
data, the angle .theta. between the straight line used for producing the
one-dimensional shading data and the longer axis of the ellipse and the
ratio of the longer axis to the shorter axis of the ellipse are stored in
the shading data memory 41 and the shading correction of image data is
effected based thereon. However, instead of the ratio of the longer axis
to the shorter axis of the ellipse, the ratio of the shorter axis to the
longer axis of the ellipse can be stored and the shading correction of
image data be effected based on the stored data.
Further, in the above described embodiment, although the angle between the
straight line used for producing the one-dimensional shading data and the
longer axis of the ellipse is obtained and stored in the shading data
memory 41, the angle between the straight line used for producing the
one-dimensional shading data and the shorter axis of the ellipse can be
obtained and stored in the shading data memory 41 and the shading of image
data be corrected using the stored data.
Furthermore, in the above described embodiment, although the bit number
converting section 43 is provided for converting the bit number of the
shading-corrected image data from fourteen bits to sixteen bits, it
suffices to increase the bit number of image data and it is not absolutely
necessary to achieve the increase by producing image data with fourteen
bits and converting the bit number of the image data to sixteen bits.
Further, it is not absolutely necessary to provide the bit number
converting section 43 in order to increase the bit number of image data.
Further, although the above described embodiment was explained regarding
the shading correction of a fluorescent image and a chemiluminescent image
produced by the CCD 6, the present invention can be widely applied to the
shading correction of images produced by two-dimensional sensors other
than a CCD such as a MOS-type sensor.
Moreover, in the above described embodiment, although the cooled CCD camera
1 is used, in cases where weak light such as fluorescent light or
chemiluminescent emission need not be detected, it is possible to use a
CCD camera having no cooling means to produce image data and to effect
shading correction thereon.
Further, in the above described embodiment, although the first blue light
emitting diode stimulating ray source 21 for emitting a stimulating ray
whose center wavelength is 450 nm is used, a light emitting diode
stimulating ray source for emitting a stimulating ray whose center
wavelength is in the range between 400 nm and 700 nm may be selected and
employed depending on the kind of a fluorescent substance.
Furthermore, in the above described embodiment, the image producing system
includes the detachable filter 27 for cutting a stimulating ray having a
wavelength in the vicinity of 450 nm and is constituted so as to detect
very weak chemiluminescent emission by removing the filter 27 and produce
a chemiluminescent image. However, it may be constituted so as to produce
only a fluorescent image by fixing the filter 27 to the front surface of
the camera lens 16.
Moreover, in the above described embodiment, although the blue light
emitting diode stimulating ray source 21 is provided, in the case where
the image producing system is used to detect chemiluminescent emission and
produce only a chemiluminescent image, the blue light emitting diode
stimulating ray source 21 is unnecessary and the filter 27 is also not
necessary.
Further, in the above described embodiment, the cooled CCD camera 1 is
formed with heat dispersion fins 15 over substantially half its length for
dispersing heat released from Peltier element 8, it is possible to form
the heat dispersion fins 15 on the periphery of the cooled CCD camera 1
over its entire length and the arrangement of the heat dispersion fin 15
on the periphery of the cooled CCD camera 1 may be arbitrarily determined.
Furthermore, in the present invention, the respective means need not
necessarily be physical means and arrangements whereby the functions of
the respective means are accomplished by software fall within the scope of
the present invention. In addition, the function of a single means may be
accomplished by two or more physical means and the functions of two or
more means may be accomplished by a single physical means. For example,
although in the above described embodiment the data processing section 40
performs the mapping of two-dimensional shading data and production of
one-dimensional shading data as well as shading correction of image data
using shading correction data, the mapping of two-dimensional shading data
and production of one-dimensional shading data, and shading correction of
image data using shading correction data may be performed by separate
means.
According to the present invention, it is possible to provide an image
processing apparatus which can simply correct the shading of an image
produced by a two-dimensional sensor by converging onto the
two-dimensional sensor light through a lens.
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